1. Field of the Invention
This invention relates to tensioning apparatus for tensioning one or more ropes in a paper-making apparatus to facilitate threading a paper web through the paper-making apparatus. In order to locate a web of paper in proper position for processing through a paper-making apparatus, a web or sheet of paper is directed by means of one or a pair of endless ropes around multiple rolls located in the paper-making apparatus for processing the web into rolled paper. Although a single rope may be used in certain applications of the paper-making machine, it is more common to use a pair of parallel ropes, each carrying the paper web. The rope typically has a diameter of about one-half inch and is usually constructed of nylon, sisal or other natural fibers having sufficient strength to maintain a desired structural integrity as the rope or ropes traverse the multiple rollers in the paper-making apparatus. Because of the nature of operation of the paper-making apparatus and the construction of the ropes, the ropes stretch during operation, typically from about seven percent to about ten percent of their original length and each rope may be from approximately two hundred to about four hundred feet in length, thereby providing a significant problem of stretch over a period of time as the rope is used to support the paper web in the paper-making apparatus.
2. Description of the Prior Art
Various types of rope tensioning apparatus have been utilized in the prior art to stretch one or more ropes used in supporting a paper web in a paper-making apparatus and in similar equipment requiring the tensioning of ropes or cables. Typical of these patents is U.S. Pat. No. 1,826,103, dated Oct. 6, 1931, to W. J. Trempe. The Trempe automatic compensator for traveling felt in paper-making machines includes an automatic compensator which maintains relatively constant tension in a traveling felt of variable length. The automatic compensator includes a pair of tracks, a sheave having a groove in the periphery thereof guided on the tracks, a shaft upon which the sheave is rotatably mounted and a roller over which the felt is guided, the roller being mounted on the shaft. The automatic compensator is designed to automatically vary the position of the sheave to maintain substantially constant felt tension. U.S. Pat. No. 3,643,497, dated Feb. 22, 1972, to George W. Lecompte details a "Tensile Loading Apparatus For Moving Wire". The apparatus is designed to test the tensile strength of moving wire and includes a main pulley having a pair of grooves and a free pulley biased away from the main pulley for leading wire in a loop from one main pulley groove to the other. Guides for guiding the wire to and away from the main pulley assure a 180-degree wire wrap about each main pulley groove. This wrap facilitates a high testing tension in the loop that extends about the free pulley, while only a low tension exists prior to entering on the main pulley and after leaving it. A "Dancer Roll Assembly" is detailed in U.S. Pat. No. 4,288,014, dated Sep. 8, 1981, to Jack Par Evers. The patent details a pair of dancer roll assemblies disposed in side-by-side relationship, each including an upper shaft and a lower shaft having spaced-apart sprockets which are vertically aligned. The assemblies receive a pair of belts which carry a dancer doll for vertical movement under the influence of a tensioned web passed around the dancer roll. The upper shaft is a control shaft and is connected to a pneumatic control motor which resists the rotation of the shaft and thus, the upward movement of the dancer roll. The tension on the web is controlled by controlling the air pressure in the pneumatic control motor. U.S. Pat. No. 5,375,753, dated Dec. 27, 1994, to Thomas E. Barthauer et al, details a "Tensioning Apparatus For Web Threading Endless Rope". The rope stretcher is designed for use in a paper-making machine and includes a beam having parallel flanges forming tracks which are engaged by guide wheels supporting separate carriages. The carriages support corresponding rope sheaves for free rotation and a pair of fluid cylinders are mounted on the beam and have piston rods connected directly to the corresponding carriages. The rope sheave on each carriage has at least two peripheral grooves to receive a double loop of the rope and the frame supports a corresponding multiple groove sheave for each of the carriage sheaves and for also receiving a double loop of the rope. U.S. Pat. No. 5,377,892, dated Jan. 3, 1995, to Charles D. Kimball, discloses a fluid pressure tensioning apparatus for a web threading endless rope. The device includes a beam having a flange forming a track which is engaged by guide wheels supporting a pair of separate carriages. The carriages support corresponding rope shields for free rotation and a pair of fluid cylinders are mounted on the beam and enclose pistons connected by a corresponding piston rod directly to the corresponding carriages. Operation of the fluid cylinders is effected by a suitable fluid tension in the rope sheaves after the tensioning apparatus is installed in a paper-making machine. A serial accumulating system for filamentary material is detailed in U.S. Pat. No. 5,413,264, dated May 9, 1995, to Frank W. Kotzur et al. The winding accumulator system is designed for controlling the storage of filamentary material between a source of material and a winding receptacle and includes multiple, serially interconnected accumulator units for storing the filamentary material. The movement of the filamentary material is varied between the accumulator units and the movement varying device to limit the change in tension of the filamentary material with changes in acceleration or deceleration of the filamentary material caused by a change in the input or output of filamentary material to or from the accumulator system. U.S. Pat. No. 5,482,266, dated Jan. 9, 1996, to Takemoto et al, details a "Paper Conveying Apparatus Having A Belt Tension Adjusting Mechanism". The belt tensioning adjusting mechanism detailed in the patent includes a belt tension adjusting pulley, over which the endless belt is placed; a plate having multiple recesses, in which a rotary shaft of the belt tensioning adjusting pulley is received; a handle having a pin provided at one end, which pin engages the recess; and a linking member connected at one end with the rotary shaft of the belt tension adjusting pulley and connected at the other end with an intermediate portion of the handle.
It is an object of this invention to provide a new and improved tensioning apparatus for tensioning one or more ropes carrying a paper web in a paper-making apparatus or machine, which tensioning apparatus utilizes one or more rodless cylinders and at least one cooperating pair of sheaves for each rodless cylinder, one of which sheaves in each cooperating pair is connected to the piston in the rodless cylinder for tensioning or reducing tension on the rope or ropes.
Another object of this invention is to provide a new and improved rodless cylinder rope tensioning apparatus for tensioning one or more ropes that carry a paper web in a paper-making apparatus, which apparatus is characterized in a preferred embodiment by at least one rodless cylinder fitted with a freely-rotating guide sheave and a tensioning sheave attached to the piston in the rodless cylinder for effecting tension on the rope threaded across the freely-rotating guide sheave and around the tensioning sheave.
Yet another object of the invention is to provide a new and improved rodless cylinder rope tensioning apparatus which is characterized in a most preferred embodiment by a pair of rodless cylinders, each fitted with a rope tensioning sheave on a corresponding piston thereof and mounted in substantially parallel relationship with a guide roller provided substantially in alignment with the rope tensioning sheave to guide the ropes over the respective guide rollers and rope tensioning sheaves and facilitate selective tensioning in each of the ropes by operation of the respective rodless cylinders.